A comprehensive study of the ethics of killing in cases in which the metaphysical or moral status of the individual killed is uncertain or controversial.

Among those beings whose status is questionable or marginal in this way are human embryos1 and fetuses2, newborn infants, animals, anencephalic infants, human beings with severe congenital and cognitive impairments, and human beings who have become severely demented or irreversibly comatose. In an effort to understand the moral status of these beings, this book develops and defends distinctive accounts of the nature of personal identity, the evaluation of death, and the wrongness of killing.

The central metaphysical claim of the book is that we are neither nonmaterial souls nor human organisms but are instead embodied minds. In ethical theory, one of the central claims is that the morality of killing is not unitary; rather, the principles that determine the morality of killing in marginal cases are different from those that govern the killing of persons who are self-conscious and rational.

Another important theme is that killing in marginal cases should be evaluated in terms of the impact it would have on the victim at the time rather than on the value of the victim's life as a whole. What primarily matters is how killing would affect that which would be rational for the victim to care about at the time of death.

By appealing to various foundational claims about identity, death, and the morality of killing, this book yields novel conclusions about such issues as abortion3, prenatal injury, infanticide, the killing of animals, the significance of brain death4, the termination of life support in cases of persistent vegetative state5, the use of anencephalic infants as sources of organs for transplantation6, euthanasia, assisted suicide, and advance directives in cases of dementia.

In particular, the book defends the moral permissibility of abortion7, infanticide, and euthanasia in certain cases and argues that brain death8 is not the appropriate criterion of death either for a person or a human organism.